Very solid lockup and rail - Samson STAR-C Carbine-Length Free-Floating Rail for AR15 - Standard 7in. Rail

I decided to go with Samson again after success with a larger Star Series. Expensive but robust. It lines up perfectly and locks into place with a very secure system. I like it so much that soon I will purchase a second for another upper with a A2 front sight post.

If your looking for a quad rail with a very secure free float design then choose this. It was either this or another RIS 2 Daniel Defense. Samson has its place in my safe for a good reason.